Two things - if you don't know the basics of a unix shell syntax (having a space in the right place matters, punctuation like / matters) don't do step 2 unless you can afford to re-install everything again - the rm command is unforgiving - delete the wrong file or directory with rm -rf and the mac won't boot. You can be more secure by using the srm command instead of rm and it will slowly shred the files - I use srm -sz -rf instead of rm -rf below to shred once and then zero out (which ends up being two passes and then a delete - plenty secure for my needs and not as slow as the default 35 pass overwrite before the delete)
Do make sure the person buying the machine knows what they are getting recovery disks for. It's really nice to make a test account to run all the updates rather than hand them the Snow Leopard disk.
Set up your Snow Leopard Mac to add one admin account named test with no password and delete any other accounts using the test account. Reboot into single user mode by holding command + s and type these exactly:
/sbin/mount -uw /
cd /var/db
srm .AppleSetupDone
cd dslocal/nodes/Default/users
srm test.plist
cd /Users
rm -rf test
halt
You can now boot the mac to see the setup welcome movie plays and quit the assistant a few steps in using command + q when it starts asking name questions and it will shut down with no account created but all the applications preserved. It will remember your wifi settings, so delete those before starting step 2 or use ethernet/a safe public wifi to run updates if you're worried about that sort of thing.
Note, some of the info in this answer was cribbed from here:
Mac OS X 10.6 Snow Leopard was the last OS to support 32 bit CPU architectures, like the Core Solo, and Core Duo (not Core 2 Duo) processors. Note that it's entirely possible to have a 64bit processors like the Core 2 Duo, and still have a 32bit EFI firmware, so the CPU alone isn't the sole indicator of your systems capabilities in this respect.
This is how you end up the situation of having a 32 bit kernel, that is held back by the EFI, running on a 64 bit CPU, which is capable of running a 64bit application stack so long as it is not dynamically loading any kernel modules etc. The application isn't wholly tied to the kernel, and is capable is independent running in a different state to the kernel if required. Same way an app can run 32bit on a 64bit kernel...
To be honest, the number of people with a Core 2 Duo or above but with a 32bit EFI are relatively limited, and you are unlucky if you are one of those people that has, say a Macbook from 2007/8 when this was common. The 64bit EFI was introduced in a staggered way across the range so it's not simple to pinpoint what date it was common across all formats.
You can check your machine’s EFI by entering the following command in Terminal:
ioreg -l -p IODeviceTree | grep firmware-abi
It will return either “EFI32″ or “EFI64.”
In addition, some perfectly capable machines still only boot into 32bit mode kernels, even when they are capable, although you can force a 64bit kernel by holding down the 6 and 4 keys on boot.
OS News notes that only Macs with a 64-bit EFI are able to boot the 64-bit Snow Leopard kernel and kexts; an artificial limitation imposed by Apple, even though a 32-bit EFI can boot a 64-bit kernel “just fine.”
What’s worse is that even if your MacBook (non-Pro) has a 64-bit EFI, it will only be able to boot the 32-bit version of Snow Leopard because of a limitation that Apple imposes on MacBooks. The biggest roadkill on Route 64 is the original Mac Pro (which was discontinued January 8, 2008) it won’t be able to boot the 64-bit kernel and drivers either.enter link description here
Best Answer
64-bit apps have been fully supported since Leopard (OS X v10.5), and 64-bit non-GUI programs since 10.3. The only thing 10.6 added was that Apple included a 64-bit kernel (which is a completely separate thing), and included 64-bit code in (almost) all of the programs they ship with the OS.
OS X uses a "fat" binary format, which allows a single program to include multiple CPU-architecture versions of itself; when it's run, the OS picks the "best" version of the program, and runs that. For instance, on a 64-bit capable Intel Mac, it'd look for a 64-bit Intel version first; if that wasn't available, it'd look for a 32-bit Intel version; if that wasn't available, it'd look for a 32-bit PowerPC version and run that under the Rosetta emulation/translation system.
Net result: many of your programs are probably already 64-bit capable, and have been running in that mode for a while now. Some may not be, in which case they'll keep running just fine in 32-bit mode. It's all remarkably transparent.
If you want to know which of your programs support 64-bit mode, run the System Profiler utility, and select Software -> Applications from the sidebar; it'll list all the programs it can find, along with whether they're Intel-only, PowerPC only, or Universal (both), and whether they have Intel 64-bit support. You can also use Finder's Get Info on a program; if it has an "Open on 32-bit mode" option, that program includes both 32- and 64-bit versions of itself (and that option will let you override the OS's ideal of the "best" version).
Now, to answer your more direct question: I don't know about Chrome, but Firefox version 3.x comes in a 32-bit only binary; version 4 comes with both 32- and 64-bit. Either one will work fine.